FUR SEAL INVESTIGATIONS 

 PRIBILOF ISLANDS, ALASKA, 1962 



by 



Alton Y. Roppel, Ancel M. Johnson, Richard D. Bauer, 

 Douglas G. Chapman, and Ford Wilke 



ABSTRACT 



From 2 July to 5 August and during various periods from 13 August to 19 

 September when female seals were killed, 43,203 male seals were taken on St. Paul 

 Island and 10,477 on St. George Island. The peak of the kill occurred from 22 to 26 

 July. Age classification in percent was: St. Paul, age 2-4, age 3-61, age 4-33, age 

 5-2; St. George, age 2-6, age 2-56, age 4-36, age 5-2. The kill was 15 to 20 percent 

 less than predicted for 1962. The forecast for 1963 is 59,000 males if the kill is 

 terminated 31 July and 72,000 if terminated 15 August. The pup population on the 

 Pribilof Islands for 1959 was estimated to be 838,000. Tag ratios from fall sampling 

 of pups produced a low estimate for 1962 (382,000). Harem and idle bulls counted 

 were 12,674 and 11,750, respectively. A total of 43,760 females were removed from 

 the herd. Fifty-five percent of the females taken in August were ages 3-5; in Sep- 

 tember these ages made up 24 percent. The percent of post partum females in- 

 creased when animals were taken on rookeries and when the proportion of older ani- 

 mals increased. A total of 3,718 tagged seals, including 2,417 with checkmarks only 

 and 20 tagged on Soviet islands, were recovered. Fifty thousand seal pups and 839 

 yearlings were tagged. Land pup mortality was 53,748. Untagged pups were heavier 

 than tagged pups from early September to late October. Weights were significantly 

 different in early September only. Pups gained 3.5-4.0 kilograms from early Sep- 

 tember to late October. Seal pups are infected with the intestinal phase of hookworm 

 by ingesting the parasite with milk. Seals of all ages harbor a tissue phase of hook- 

 worm in their belly blubber. 



INTRODUCTION 



Beginning in 1956 the Pribilof seal herd has 

 been subjected to a program designed to reduce 

 the number of pups produced annually with 

 the expectation that as the number was re- 

 duced the rate of survival would improve. 



During the 7-year period, over 225,000 fe- 

 male seals have been taken on the Pribilof 



Note. --Alton Y. Roppel, Ancel M. Johnson, Richard 

 D. Bauer, and Ford Wilke, Wildlife BtoZogists, Bureau of 

 Commercial Fisheries, Marine Mammal Biological 

 Laboratory, U.S. Fish and Wildlife Service, Seattle, 

 Washington; and Douglas G. Chapman, Laboratory of 

 Statistical Research, University of Washington, Seattle, 

 Washington. 



Islands. Natural mortality, which was in- 

 creased in intensity in some of these years, 

 also reduced the number of females an addi- 

 tional indefinite amount. The combined effect 

 of these reductions appears to show: in aban- 

 doned rookery areas, in greater difficulty in 

 finding off-rookery groups of females, and in 

 the need for more effort to tag a specified 

 number of pups. These changes are somewhat 

 subjective and not readily measurable. 



Estimates of the number of pups produced, 

 based on tag recoveries at ages 3 and 4 years 

 for seals born up to 1959, do not suggest that 

 up to that year a substantially reduced number 

 of pups were being produced. 



